Our philosophy was that the shell had to perforate the target intact before detonation, something that could not be guaranteed with the German shell, even against the very thin aircraft skins of WW-II! Any even cursory examination of damage pics from then would show many partial detonations, or failures to detonate at all.

A conventional shell might make exit holes on the far side of the fuse, away from the point of impact Most of the fragments from the M-Shell would fail to perforate the skin of the plane more than a foot or so from the point of detonation and show up in the pictures as many small dents with some partial perforations. The absence of fragmentation near the impact point proves the type as AP. While 20 mm AP had little trouble perforating ALL armor on any plane, HE/HEI/HE-T and their respective fragments would not perforate any armor at any point, usually owing to fuse initiation on the plan's skin at any distance before the armor plate. Things like the outer case of Radios, air bottles and instrument panel plates would stop all fragments from small caliber bursting munitions. That is why post war, the VERY thin wall M-Shell construction type was eventually abandoned by every one. The closest imitator is, IIRC, the British Mk-Z(50) 30 mm shell for the Aden Revolver gun and the shell body walls are more than twice as thick as the German war time M-Shell bodies. IIRC, the Mk-Z was discontinued in the mid to late sixties?

It appears to me from this excerpt that the different types of M-ammunition are not particularely well understood. The function of burst is entirely dependent on the type of fuse used. There are contact explosion (virtually non-delay) fuses, advanced detonation fuses (short delay), time fused and condition fuses aviable for the M-Geschoß (such as a hydrostatic fuse which would only detonate once the tip of the projectile enters a liquid filled space / fuel tank). Filling was also different between HE-only and HE-I filling as well as compressed HE-filling (MX-Geschoß). For the 20mm M-round, more than 10 service types existed. The 30mm was also provided with a reduced capacity but more streamlined version, Ausf. C. The MG-213C/30mm, which was selected as standart LW fighter gun by the end of war (entering production on march 45 but only fitted in some very few Fw-190D13 before end of hostilities, one of them survived in the NASM) was provided with a 30 x 85 cartridge and Ausf. C mine round. The gun and projectile were copied and improved upon after ww2 in the UK with the slow velocity ADEN´s mentioned above and considered to be very successful against then in service A/C. However, A/C construction changed in about this period and the missile made it´s advent.

The effectivity of high capacity mine rounds was evaluated after war in the US, in connection with standart and experiemental US gun/ ammunition. The relevant primary source is Weiss/ Stein, Airplane Vulnerability and Overall Armament Effectiveness, Memorandum Report No. 462, Army Ballistic Research Lab Aberdeen (1947).

In these static trials, a substantial number of airplanes, engines (including some of the then new jet-engines) and dummies were expanded to assess the capabilities of different types of ammunition against some rather sturdy US aircraft types: F6F, P-47, B-26 under varying ranges, fuel load conditions and directions.In these trials, the 30mm mine round Ausf. A was considered to have the same one-hit kill probability as US 37mm M4 ammunition on target. While blast may not penetrate armour plate, there is little area covered by armour plate on airplanes. The blast effect is also entirely unrelated to impact velocity (unlike AP) and the excess blast effect caused by mine rounds was considered sufficient to cause airframe failure in as many cases as the twice as heavy US 37mm HE ammunition. One has to factor in that the tested for airframes had a structural layout with load carrying frames rather than full stressed skin, which appeared in the Jet Age.

In this case, the high probability of "B" kill was caused by excess structural damage to the airframe caused by blast effect -the probability of structural failure was four to five times as large as with the 37mm HE-I, though probability of catastrophic engine failure was only 8% compared to 19% for the 37mm.

Other planes yielded different results, sometimes 30mm mine was worse than 37mm, sometimes not. The averaged effectiveness was about the same. Thus the effect on target for a 300gr. mine round was entirely comparable to a 612gr., 37mm HE-I projectile.Against B-25 from front and below, the one hit "B" kill probability was 74% for 30mm mine round and 37mm HE-I. Thus, it´s not a failure of effectiveness against the then in service targets that removed the mine round but a general change of target structures with Mach 2 airplanes, capable to deal with more structural damage which made their advent in the 60´s.In ww2, the mine round was deadly effective against airplane targets.